It is well known in the vacuum cleaner art to provide a suction nozzle which is movable across an object to be cleaned. The suction effect created at an opening in the nozzle results in the removal of free dirt particles accumulated on the object. However, ground in dirt is frequently encountered when cleaning carpets or other textured surfaces, and reliance on simple suction for removal of such ground-in dirt has proven to be unsatisfactory.
Accordingly, effort has been made to provide vacuum cleaners with an effective means to beat the carpet surface to dislodge ingrained dirt particles. Such beaters are often located on the vacuum cleaner nozzle head, so that dirt can be dislodged and instantly removed by simply moving the nozzle head across a soiled carpet surface. The earliest known beaters are mechanical beaters, which include protruding elements that physically strike the carpet surface to loosen dirt particles as the beater rolls across the carpet. An example of a mechanical beater is disclosed in U.S. Pat. No. 6,108,853, which includes a cylindrical rotatable beater brush having a plurality of extending resilient bristles and prongs that physically beat the carpet as the nozzle head is moved.
Later, “sonic” beaters were developed, which vibrate as they move across the carpet surface. For example, U.S. Pat. No. 6,161,251 to Lee et al. uses a mechanical vibration generating device that vibrates using air sucked though a supplementary suction hole to beat the carpet. In various embodiments, the vibration generating device can be used to vibrate the nozzle body which in turn vibrates the surface to be cleaned or the vibration generating device can directly beat the surface. Also, U.S. Pat. No. 2,932,054 to Lichtgarn discloses a vacuum cleaner in which the vibration of disks produces a vibrating column of air that loosens dirt in a carpet. Similarly, U.S. Pat. No. 5,400,466 to Alderman et al. discloses an air vibration suction nozzle that includes a speaker that vibrates the suction air and a means for adjusting the frequency and amplitude of the airwaves produced by the speaker.
Although sonic beaters for the most part avoid physical damage to a carpet often caused by mechanical beaters, they are not as effective in dislodging dirt on the surface of a carpet pile. At the same time, mechanical beaters are not as effective in removing particles embedded deeply in the carpet pile. Also, mechanical beaters tend to push dirt particles down into the carpet, thereby making it more difficult to effectively clean the carpet. Accordingly, there is a need for a beater construction that can provide a vacuum cleaner with a more thorough cleaning action.